In the prior art, there are known several methods for forming structures that are of very small dimension (nanostructures); many methods of this kind make use of AFM-like devices, i.e. devices which mainly consist of a tip which is mounted on a cantilever, the latter being relatively movable with respect to a substrate. Particularly, nano-lithography by AFM has a high potential due to the ability of this technology to create structures in the order of nanometers, which dimension is even smaller than the wavelength of conventional laser light.
However, a problem that usually occurs in these known methods is the wear of the tip of the AFM; this is because the nanostructures are formed by applying current to the tip in order to modify the structure of a photoresist layer, this current destroying the apex of the tip after relatively short time. A further disadvantage of these conventional methods has to be seen in that the writing into a layer of polymer by an AFM device does not give satisfactory results with respect to the resulting pit size.
Furtheron, in most of these prior-art devices, the application of force writing has been used in order to form the structures. However, the process speed is relatively slow in this approach because the relatively soft cantilevers of the AFM devices have to be deformed to a large extent in order to obtain a force of sufficient strength. Thus, the formation of the nanolithographic structures takes a very long time.
Accordingly, it is the object of the present invention to provide a method of forming ultrasmall structures, i.e. structures having dimensions in the order of nanometers, which both allows to form extremly small pit sizes and to avoid wear of the tip. When in the following it is referred to avoidance of tip wear, also a reduced tip wear with respect to known methods shall be implied.